Talk

Why will you be asked about his performance? What about his manager? If they want to dig for something on him, they need to introduce 360degree appraisals. That is a very awkward situation with his wife though!!

Sorry but I think you need to tell the truth - or some version of it.
Don't complain too strongly though or they might label you as overcritical and difficult to manage.
Even if they decide not to keep him on in the long term, he will have rights to redundancy pay etc and the opportunity to find a new career that he is better suited to.
Damn him with faint praise, warmly express admiration for things that aren't significant, and suggest that he could benefit from further training in areas a/b/c which are critical to company success.

How much anonymity will you have?

Anyway, I would treat it as you would any other performance review - so even if you're not in a position to give performance reviews currently, think of it as practice for the future. There are plenty of articles online on how to give constructive feedback - and you should aim to give constructive feedback where possible and be positive where you can - there must be something he's good at (this is what I keep telling myself about the twatty manager I have to deal with, and I have to admit, I struggle to work out what his good points are.)

Focus on the behaviours he shows. If he's unreliable, how does he show that? Does he miss deadlines? Not reply to mails by the time he said he would? Tell you one thing, then change his mind? Not state clear goals and requirements? Try and show how that affects people in the team - time wasted working on the wrong priorities, time wasted on something which then goes in another direction (recognise that sometimes this will happen anyway, because that's the way of the world, but you can usually tell whether it's because of internal or external factors.) How does he fail to be a team player?

Give specific examples as much as possible - if he does stay, then they've got something to work with on his development plan (assuming you have something like that).

The fact you despise him isn't really relevant. You should be focussing on his behaviours, rather than his personality, although obviously there will be links. You should try to be objective, rather than personal.

In my humble opinion he is the least person on earth I would ever want to work for, the most unreliable, twattish manager I have ever met in my life. All the problems in our department are down to him and his inability to be a team player. I can't wait for the day I will be working for somebody else

Would you really want to give him a "good reference" just because you're friends with his wife? If he's that bad?

I'd say doing so would damage your own credibility. Others will also have noticed how bad he is, including probably his seniors. No one is going to dismiss him purely on the say so of one of his direct reports anyway. If he loses his job it won't be your fault, because the chances everyone else thinks he's absolutely wonderful are slim to none.

No one is going to dismiss him purely on the say so of one of his direct reports anyway. If he loses his job it won't be your fault, because the chances everyone else thinks he's absolutely wonderful are slim to none.

This is very true. If he does lose his job, it won't be because Pippidoeswhatshewants rated him badly, but because a large selection of people did so. A bad rating from a single direct report will be taken with a pinch of salt as a single employee might just have an irrational grudge, but it will be taken seriously if corroborated by others.

As above, try to give a balanced view, complementing and praising his strengths where possible but not lying about or hiding his weaknesses.

Thanks for some good ideas. I shall stick to praising what little there is to be praised. If they start to drill down into specific department failings it will all blow up in his face anyway.

I was honest, kept it to the facts that were detrimental to the company and tried my best not to swear

I liked that manager as a person but she was a shit manager and shouldn't have been given such a large team. The directors must have had the same feedback from others as she was performance managed out and a new manager brought in.

The feeling amongst the teams is visibly better and it's a nicer place to work now.

As I said, I think that plan may well damage your own credibility OP, particularly if, as you say, they are likely to find out anyway.

The second they start asking me about why projects weren't delivered on time or any other specific it's all going to come out anyway, flowery. I can't lie... and I don't want to look like a complete idiot myself, I am not going to cover up his shortcomings if this means it will look like my fault!

Well indeed!

I think you need to pick the most significant issue and comment on that. So mention all his positives and then one major weakness.

I think your plan is a dangerous one. What is the format for this review? A combination of written and interview? Just interview?

You plan to stick to a narrow list of positives but not mention any negatives until questioned. What if they don't ask the right questions? What if they see the negatives coming out later as backpedaling / arse-covering?

I am looking for a new job anyway, I can only hope that I can get out before the shit hits the fan.
I think I will just have to tell them how we do things and they can easily draw their own conclusions.